Typical roped or hydraulic elevators in current use consist of a cab which is moved vertically within a hoistway shaft by means of an external mechanism, such as a traction machine for roped elevators and an hydraulic piston and pump for hydraulic elevators. The location of the machinery associated with such external hoisting machines can be problematic in certain types and arrangements and buildings.
Designers have attempted to address the these problems by proposing self-propelled elevators in which the lifting mechanism is integral with the elevator car, thus avoiding the need for a machine room or other designated space to house the elevator lifting machinery. Various prior art designs have utilized rack and pinion arrangements in which a geared pinion on the elevator car engages a linear rack disposed vertically in the hoistway, linear induction motors wherein the primary and secondary armatures are disposed on the elevator car and hoistway, respectively, and other means which will readily occur to those skilled in the art. Each has various drawbacks in terms of speed, power consumption, ride quality, etc., and none have achieved wide-spread acceptance or use.